Field Day is a ham radio contest conducted by the ARRL the fourth weekend every June.

Field Day stresses emergency preparedness. Frequently, entire radio clubs get involved, and take "Field" Day literally, erecting numerous towers, each bearing several antennas, in a field. Generators provide power to ham radio [transceivers].

The goal of Field Day is to work, or contact, as many stations as possible throughout the 24-hour duration of Field Day. The Field Day exchange is one's callsign, along with the number of stations in simultaneous operation, proceeded by a letter (A-F) designating the method in which the stations are being powered, such as by generator, solar power, or conventional mains AC.

Unlike most other contests, Field Day is rarely a single-man operation. In fact, Field Day is frequently used to attract significant publicity to what ham radio is about. Some clubs will demonstrate a wide range of technologies, including single sideband voice, Morse code, and a number of digital modes including APRS, packet radio, as well as satellite communications.